Forum Discussion

alex_luna_23167's avatar
alex_luna_23167
Icon for Nimbostratus rankNimbostratus
Feb 15, 2017

Configuring DNS cache global settings

In this Feature, " In the Maximum TTL field, type the number of seconds after which you want the system to re-query for resource records. "

 

i need some examples to understand this option, because it says "This setting allows the system to re-query for resource records sooner than the owner of the records intended."

 

I really appreciate your help.

 

Thanks in advance

 

BIG-IP DNS
security

1 Reply

  • crodriguez's avatar
    crodriguez
    Ret. Employee
    Feb 15, 2017

    Normally, a resource record obtained via recursive resolution remains cached for the TTL supplied in the query response. On BIG-IP DNS, the TTL may be overridden by the value in the Maximum TTL setting. The BIG-IP system deletes records from cache when the TTL specified in the response is reached or when the Maximum TTL is reached, whichever occurs first.

     

    As mentioned in K14922: Configuring the DNS cache TTL statement for the BIG-IP DNS system, "In certain cases, you might want to change [Maximum TTL] for the BIG-IP system. For example, setting [Maximum TTL]... to a lower value can have one or more of the following benefits:

     

    • It mitigates DNS cache abuse (for example, ghost domains)
    • It reduces "bad" records caching (for example, poor hostname migration planning may require you to flush the bad records from the DNS cache)